This present invention relates to a method for the recovery of lipids from bird tissues.
Birds possess varying amounts of fat tissue under their skin and in their peritoneal cavity. The recovery of the oil or lipids from the lipid containing tissues of birds is desirable for various uses such as a nutriment, nutraceutical or cosmetic.
The known methods for recovering lipids from lipid containing tissues of birds usually comprises the heating of the lipid containing tissues once they have been removed from the bird.
In general, the fatty tissues from birds which are raised for food purposes are collected in slaughterhouses. Today, fat in generally has a bad reputation and accordingly it is frequently considered as waste or a low value product. This reputation derives in part from the fact that the fats are often contaminated by bacteria such as salmonella. Accordingly, often the fats are frequently subjected to a heat treatment and at a relatively high temperature to destroy any bacteria. This results in oxidation of the unsaturated lipids.
Certain oils derived from certain birds are considered to have a higher value. Thus, emu oil is taught in the art to have certain desirable characteristics. One desirable characteristic of emu oil is that it is particularly low in cholesterol.
It is an object of the present invention to provide a method for the extraction of lipids from lipid containing tissues of birds and which preserves the quality of the lipids.
According to one aspect of the present invention, there is provided a method for the extraction of lipids from lipid containing tissues of a member of the bird species, the method comprising the steps of comminuting the lipid containing tissues, placing the comminuted lipid containing tissues in a solvent for a period of time sufficient for at least a portion of the lipids in the lipid containing tissue to dissolve in the solvent to thereby provide a liquid fraction and a solid fraction, separating the liquid fraction from the solid fraction, and removing the solvent from the liquid fraction to thereby recover a lipid rich component.
The method of the present invention may be applied to lipid containing tissues of any bird from which it is desirable to recover high quality lipids. Particularly preferred are methods supplied wherein the bird is a ratite, a gallinaceous bird or an anatidae (duck and geese family). Ratites include the emu, nandou, and ostrich, all of which have had oils used for their health benefits by aboriginals in Asia, Africa and South America.
As practiced commercially, the bird would be bled properly and the fat removed and cooled. Typically, the fat may be frozen to facilitate the handling of the tissue.
The step for comminuting the lipid containing tissues may be carried out by any conventional means. Thus, one would process the tissues at ambient temperatures. The tissues may be comminuted by means of a grinder or other suitable means.
The comminuted lipid containing tissues would then be subjected to extraction using a suitable solvent. Particularly preferred are acetone and ethyl acetate. The extraction would be done at a relatively low temperature and preferably between 4xc2x0 C. and 25xc2x0 C. The temperature is not a critical parameter; a higher temperature will increase the ambient level of the vapors of the solvent.
The volume/weight ratio of solvent to the lipid containing tissues may vary. Generally, the solvent tissue volume/weight ratio should be at least 3:1 and a preferred ratio is between 3:1 and 9:1.
Preferably, the solvent tissue mixture is agitated and any suitable means may be employedxe2x80x94a container equipped with agitation paddles as is well known in the art will ensure an efficient mixing.
The extraction time period may vary; generally, a period of time greater than 20 minutes has been found to be required.
Following, the extraction, the liquid fraction and solid fraction need to be separated. Again, many apparati are known in the art and to this end, one may use an apparatus for centrifuge. Alternatively, filtration could be utilized and in some instances, a combination of the methods can be appropriatexe2x80x94i.e. an initial centrifuge followed by a filtration. It would also be possible, where time is not a factor, to utilize sedimentation.
Following the separation of the liquid fraction and the solid fraction, the solvent will be removed to provide a lipid rich component. The solvent may be removed by known methods, including, for example, flash evaporation, straight evaporation or spray drying. The step may be practiced either in batches or on a continuous basis. The temperature can be increased up to approximately 125xc2x0 C. for a very limited period of time. This will ensure the sterilization of the oils and during a limited period of time, will minimize chemical changes in the lipids. To minimize oxidation, one could perform the step in a nitrogen atmosphere.
Optionally, one can add an antioxidant to the liquid fraction to minimize lipid oxidation. Alternatively, the antioxidant could be added after removal of the solvent. Still further, an antioxidant could be added during the extraction step. Any number of food grade antioxidants are known in the art.
Optionally, after separating the liquid fraction and the solid fraction, one may wash the solid fraction with a solvent.